1. Field of the Invention
The present invention relates to a heat sink for cooling a semiconductor element which emits much heat such as a micro processing unit (referred to as an MPU hereinafter).
2. Description of the Prior Art
Heat sinks have been used for cooling semiconductors and the like which emit much heat. Recently, in particular, a fan-motor-integrated heat sink incorporated with a small fan is used for coping with the high heat emission of the MPU etc.
Conventional heat sinks will be described hereinafter. FIG. 8 is a perspective view of a conventional heat sink and FIG. 9 is a cross sectional view of the conventional heat sink.
In FIGS. 8 and 9, reference numeral 81 denotes an MPU that is a high-exothermic semiconductor element, 82 a heat sink substrate which is mounted on the MPU 81, 83 radiator fins, 84 driving means such as a motor or the like, 85 a fan and 86 a structure such as the casing of a notebook-type personal computer etc. for defining a space above the heat sink.
The operation of a conventional fan-motor-integrated heat sink having the aforementioned structure will be described hereinafter. Heat emitted from the MPU 81 is transmitted to the heat sink substrate 82 and the radiator fins 83. Air flow generated by the fan 85 rotated by the driving means 84 is taken in between the structure and the upper surface of the heat sink as shown by an arrow A and passes among the radiator fins 83 while carrying off heat therefrom to be vented from the side surface thereof as shown by an arrow B.
The aforementioned conventional structure had a problem that it was impossible for thin devices such as the notebook-type personal computer limited in thickness to secure a sufficient space for taking in air from above the heat sink and consequently to secure a sufficient cooling performance. Although the entire heat sink may be made thin for securing sufficient space, a motor capable of rotating the fan to generate a sufficient amount of air flow for cooling the device required a certain degree of thickness because of the structure of its bearing and coil, so that the motor was structurally limited in being made thin.
An object of the present invention is to provide a fan-motor-integrated heat sink capable of effectively supplying cooling air flow to an element even if the same is a heat emitting element such as an MPU etc. employed by a thin device which cannot secure a sufficient space above the heat sink.
In order to attain the above object, the present invention obtains a sufficient space for taking in air between the upper surface of the heat sink and the casing of a device by making the height of the fan and those of the fins of the heat sink lower than the height of the upper surface of the fan driving means such as a motor which is structurally limited in thickness relative to the heat sink substrate. Furthermore, the heat sink substrate and the fins are formed such that air is vented only in one direction to compensate for the reduction of cooling performance caused by miniaturizing the fan and the fins of the heat sink substrate, and a cover is provided on the inlet side to prevent the vented air from being taken in.
This structure enables arranging a structure above the heat sink nearly as low as the height of the motor and consequently mounting the heat sink on a thin device.